Lubrication systems for internal combustion engines on passenger vehicles may be wet or dry sump lubrication systems. A wet sump lubrication system is typically used on production vehicles. Lubricant is stored beneath the crankshaft and oil pan. The oil pan needs to be large and deep in order to hold sufficient amounts of lubricant, such as oil, to lubricate the engine.
Dry sump lubrication systems utilize an external tank to store some of the oil outside of the engine. Accordingly, a large and deep oil pan under the engine is not required. Therefore, the main mass of the engine may be placed lower in the vehicle. Dry sump lubrication systems are commonly used with high-performance engines, such as racing vehicles.
In vehicles with a dry sump lubrication system, oil is pumped from the external oil tank or reservoir to bearings or other parts of the engine that require lubrication. Oil that is thrown from the crankshaft bearings during operation of the engine drains to the sump located in a lower part of the crank case. Oil received in the sump is pumped back to the oil tank by a scavenge pump. This oil contains a large quantity of entrained air, which is absorbed into the oil due to splashing during the lubricating process. Entrained air lowers the lubricating efficiency of the oil. A deaerator or air separator is sometimes provided in the external oil tank to deaerate the oil so that oil returning from the oil tank to the engine is deaerated.